Polymerizable composition



a w tress Heierence 59am" FIF'BEUE XR 21299113 I U H Patented Oct. 20,1942 v V p g UNITED STATES PATENT OFFICE POLYMERIZABLE COMPOSITIONLaurence William Cod-d, Addlestone, and Frederick Thomas Hamblin,Norton-on-Tees, England, assignors tolmperial Chemical IndustriesLimited, a corporatip n of Great Britain N Drawing. Application August16, 1939, Serial No. 290,490. In Great Britain August 19,

g 1938 4 Claims. (Cl. 360-486) v v v This invention relates toimprovements in polypolymerizabl compound at room temperature merizablecompositions and, more particularly, but which has no appreciable efiecton the polyto suchcompositions when comprising monomeric merization ofsuch compound at elevated temor partially polymerized organic compoundsconperatures. Other objects will be apparent from taining the group 5 thdescription of the invention given hereinafter.

The above objects are accomplished according to the present invention bymixing with a polyi merizable organic compound containing the ormixtures of the monomeric and polymeric 1 group forms of such compounds.I i

Proposals for the utilization of such materials CEz=C by polymerizationprocesse have suffered from I the disadvantage that th monomericmaterial always possesses a considerable tendency to polyin inhibitorproportions, a substance having an merize spontaneously so that monomercannot inhibitingv efiect upon polymerization of the oreconomically bestored for any substantial period. ganic compound at room temperaturebut which To overcome this objectiomit has been proposed loses thisinhibiting effect at an elevated tem to add to the monomer substanceshaving an inperature at which it is desired to polymerize-the hibitoryefiect upon the polymerization reaction, organic compou such ashydroquinone. Thi so-called instability in the inhibitor Thesepreviously proposed inhibitors enable the may be attained by employingan inhibitor which monomer to be stored satisfactorily but, when isvolatileat the temperature at which it would polymerization is requiredto be effected, itcan ordinarily'be desired to effect polymerization, oronly be accomplished either by the admixture of one which, at etemperature f polymerization,

suflicient polymerization catalyst to overcome the decompose into P shaving o inhibitory eifect of the inhibitor or by removal of th ine fhibitor. The .former method iswasteful since it By employing such aninhibitor, the necessity necessitates the use of increased amounts.offor adding 'a'p y Catalyst at e ime catalyst, while the latter methodis, in practice, of polymerization is avoided; as soon as theininvariably inconvenient. In certain cases, it'may hibitor isdestroyed, polymerization may be ofbe not only inconvenient butpracticall imposfected by known means using heat or light just sible tomix polymerization catalysts with 'the as if no inhibitor had beenintroduced into the material to be polymerized. Thus, for many purpymerizable compound. If des red, & P y poses it is advantageous toemploy as the polynotion ootttlyst y b p a e in ep lymerizable materiala mixture of monomer and merizable compound either at the time ofintropolymer in such proportions that the composition ducing theinhibitor or at the time it is desired is spongy or rubbery. With such acomposition to p y e the compound. If the cataly t is it is not at alleasy to admix uniformly and satis-, introduced with the inhibitor, itwill exhibit its factorily a catalyst to promote polymerization 40normal i i y esseon as the inhibitor has been and, consequently, theordinary inhibitors are destroyedf t e Catalyst is nt oduc d a r of nouse in assisting storage of such materials. the inhibitor has beedestroyed, it will simp y Even in those .cases where the polymerizablefunction as the same catalyst would function in mixture is of sufiicientfluidity to permit incorthe poly e i at f material that, d e r porationof catalysts, economy in the consumpbe n inhibited- Where ePolymerization e tion of catalyst maybe effected by the use of ly t athe inhibitor e p t in e p lythe present invention. V merizable compoundat the same time, it is neces- An object of the present invention is toprosary to select catalysts andinhibitors which do vide a means ofstabilizing polymerizable comnot tually react'with one an ther. a

" pounds so that they can be satisfactorily stored 10 The presentinvention is applicable to polywithout danger of polymerization and yetnot inmerizable compounds whether such compounds volve the disadvantagesdiscussed above when it areentirely in the monomeric state or consist ofis desired to polymerize them. A more particular a mixture'of monomerand polymer or are'in a object isto provide a polymerization inhibitorpartially polymerized state. I which will effectively inhibitpolymerization of a The inhibitors of the present invention may be usedto inhibit the whol class of polymerizable organic compounds containingthe group Prominent among such compounds may be mentioned aciylic,methacrylic, and homologous acids, their nitriles and esters, as well asstyrene, alpha. methyl styrene, and the various vinyl Secondary butylmethacrylate Tertiary amyl methacrylate Phenyl methacrylate G l y c 01monomethacrylate Glycol dimethacrylate Specific esters adapted to bestabilized in accordance with the present in- Cyclohexyl methacryl atePara cyclohexyl phenyl methacrylate Decahydro-beta-naph thol methacrylatDi-isopropyl carbinol methacrylate Furfuryl methacrylate Tetrahydrofurfuryl methacrylate Methyl acrylate Ethyl acrylate Butyl acrylate Itwill be understood that the present invention is likewise applicable tomixtures of polymerizable compounds, such mixtures being adapted onpolymerization to give interpolymers.

The choice of inhibitor and the exact proportion to be used in anyspecific instance will be dependent upon the polymerizable compound tobe stabilized and some preliminary experimental work may be necessary todetermine the optimum inhibitor and the optimum proportions forspecificcases. However, it has been found, for example, with monomeric methylmethacrylate, that all of the inhibitors given in the following tablesatisfactorily inhibit polymerizationof the methyl methacrylate nudernormal storage conditions whereas polymerization could be effected at100 C. substantially as readily as if no inhibitor had ever beenintroduced into the composition. In the following table the time takento reach a standard degree of polymerization in the various inhibitedcompositions at 100 C. is given:

Table Timie1 takten go reac a s an Composition to be polymerized 8rddegree polymerization Hr. Methyl methacrylate 1 w 30 Methyl mcthacrylatc+01% benzoic acid. .1 l '20 Methyl methacrylate +01% acetamide 1 1 30Methyl mcthacrylate +0.1% crotonic acid lllllll 1 30 Methyl methacrylate+01% ammonium carbonate. 1 40 Methyl methacrylate +01% ammonia l 50Methyl methacrylate +01% pyrrol 2 Methyl methacrylate +0.1% pipendme 2Methyl mcthucrylate +01% ammonium carbam- 2 5 ate 2 Methyl mcthacrylate+01% hexamine l 55 Methyl methacrylatc +01% aldehyde ammonia... 2

All of the above compositions were stored at temperatures up to 50 C.for fourteen days without appreciable thickening taking place. In theabove table the percentages given are by weight if th e.methvlmethacrvlate employed As those skilled in the art will understand,the proportion of inhibitor used will normally be very small although itWill be varied to some extent depending upon the inhibitor used, thepolymerizable compound being inhibited, and the particular conditions ofstorage to which the polymerizable compound is to be subjected. Anamount of inhibitor as low as 0.01% by weight of the polymerizablecompound is generally eifective for ordinary conditions although, asidefrom reasonsof economy, the proportion of inhibitor could be fargreater. That there would be any "practical reason for employing greaterthan 1.0%

of inhibitor by weight of the polymerizable compound beinginhibited, isdoubtful, although the I use of a 'greater amount of inhibitor is notex- --cluded by the present invention.

' It will be apparent that the primary advantage'in the presentinvention is that a means is provided for inhibiting polymerization ofpolymerizable compounds during storage and permitting the polymerizationof these compounds with no greater difiiculty than the uninhibitedcompounds could be polymerized. In view of the difiiculty encounteredwith polymerization of polymerizable compounds that have been inhibitedwith inhibitors heretofore known, it is obvious that this is a verysubstantial practical advantage. Further, under certain circumstances,there is no feasible means of overcoming the inhibiting effect ofheretofore known inhibitors, even if the economy of the operation wereof no importance.

The present invention is particularly advantageous in its application tothe manufacture of dentures made from polymerizable compounds. Denturesof this type are conveniently made by mixing together a monomer andpolymer and molding the mixture but, in usual circumstances, thisinvolves preserving either the monomer by itself or in admixture withpolymer for appreciable periods Without spontaneous polymerization ofthe monomer. The inhibitors of the present invention not only preventthe spontaneous polymerization of the monomer under any normal storageconditions but are of great value in that they do not complicate thepolymerization when the monomer-polymer mixture is to be molded into adenture, this molding usually being done by men not necessarily skilledin chemical manipulations.

The dentures discussed above are largely made, according to presentpractice, by molding a mixture of monomeric and polymeric methylmethacrylate and it has been found that the introductionof an inhibitorin the amount of 0.1% by weight of the monomeric methyl methacrylate,into the monomer satisfactorily inhibits it under the usual conditionsencountered regardless of whether the monomer is stored by itself or isintimately mixed with. polymer, and yet permits the molding of thedenture to proceed as simply as if fresh uninhibited monomer were used.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

We claim:

1. A composition comprising polymerizable methyl methacrylate and, as apolymerization inhibitor therefor, about 0.1%, by weight of said methylmethacrylate, of a compound from the 11.1.7.1 groumconsis il s 2i.alcetamide ammonium car- 252a eoMPosmuw-s iss,- fieisrsncie Search Rm?inhibitor therefor, about 0.1%, by weight of said methyl methacrylate ofammonia.

4. A composition comprising polymerizable methyl methacrylate and, as apolymerization inhibitor therefor, about 0.1%, by Weight of said methylmethacrylate of ammonium carbamate.

FREDERICK THOMAS HAMBLIN. LAURENCE WILLIAM CQDD.

